This invention relates generally to ultrasonic imaging and, more particularly, to creating multiple planar ultrasonic images of an object in real-time, as the ultrasonic data is acquired.
A major advantage of three-dimensional ultrasonic imaging is the ability it provides to obtain unique image planes through the volume of an object such as a human body, image planes not available through conventional two-dimensional scanning. For example, through three-dimensional imaging techniques one can look simultaneously at several different cut planes of a region of tissue to thereby observe features from different angles. Alternatively, it may be desirable in certain instances, to view an image plane at a constant depth below the object surface such as the skin; such an image plane cannot be obtained with normal two-dimensional scanning because of the orientation of the ultrasonic probe relative to the object.
Generally, three-dimensional imaging techniques work by acquiring an entire volume of data in the region of interest, and then xe2x80x9cslicing throughxe2x80x9d the data at appropriate angles to view desired planar images. Often a number of planar images can be displayed simultaneously on a computer monitor.
Prior three-dimensional ultrasonic imaging methods, however, must acquire data from the entire volumetric region of interest in order to construct three-dimensional images. These methods can typically acquire three-dimensional data at a rate of no more than one to two volumes per second. Consequently, these methods are relatively slow and not suitable for generating useful planar images in real-time, which is necessary to capture rapid changes in the region of interest. To speed up the data acquisition rate sufficiently to generate real-time planar images, the image quality or the field of view is sacrificed. This usually reduces the clinical usefulness of such images, especially in the areas of surgery, cardiology and obstetrics.
In accordance with the invention, method and apparatus are disclosed for creating multiple planar images of a volumetric region of an object without acquiring data from the entire volumetric region. In one aspect of the invention, the method includes sweeping a transducer across the volumetric region. At sampling positions during the sweep, ultrasonic beams from the transducer are transmitted into the volumetric region and intersect one or more of a plurality of surfaces to be scanned, which surfaces can be planar or non-planar. The number of transmitted beams is fewer than the number of beams that would be transmitted to scan the entire volumetric region. Echoes from the volumetric region are received at the transducer in response to the transmitted beams. From the received echoes, planar images are formed corresponding to the plurality of surfaces scanned. Because only a finite plurality of surfaces of the region are being scanned rather than the entire volumetric region, planar images of high image quality and a broad field of view can be created and displayed in real-time.
In another aspect of the invention, the method includes processing fewer echoes from the volumetric region than the echoes that would be processed to image the entire volumetric region. This variation enables the creation of planar images corresponding to buried surfaces within the volumetric region.